Tape Drives for Users

We have recently put some old tape changer in the public area for group use.

Configuration

System Drive Tape Device Changer Device Capacity Notes
tripoli ADIC 22 DLT4000 /dev/rmt/0 /dev/scsi/changer/c1t1d0 22x 20/40 GB Used to be used for roma's backups
cancun ADIC 22 DLT4000 /dev/rmt/0 /dev/scsi/changer/c1t1d0 22x 20/40 GB Used to be used for rio's backups

Tape Changer

To control the tape changer we have two programs installed:

  • MTX - a fairly low-level program for changing tapes, it's also fairly powerful.
  • tapechanger - uses TapeChanger::MTX to control the tape drive in a pretty reasonable manner (it was designed for backup use). For more information, 'man tapechanger' or 'man TapeChanger::MTX' on a Sun.

Writing to Tapes

You will probably want to write to tape with either dd, ufsdump, or gtar. I'm not (at this point) going to write out a tutorial on these commands or using them with tapes; just read the man pages (carefully!) and make sure you label your tapes properly.

Choosing which device node to use is more effort than just typing in '/dev/rmt/0'. Different flags at the end of the device name ('/dev/rmt/0n', for instance) offer different behaviours; you'll probably want to use these sometimes. Our backups have generally used '/dev/rmt/0cbn' or equivalent.

Letter Meaning Implication
n Don't rewind the tape after using it Can put multiple volumes per tape.
c Compress the data to the tape  
b BSD behaviour More-readable by a variety of OS's.

More information can be found on the mtio web page.

Getting Tapes

We currently have ~200 DLT4000 tapes left over from when we used regular DLT tapes for backups. Each one will store 20GB uncompressed, or (nominally) 40GB compressed, when used on the public drives. I will give them out to users as necessary, but I must personally approve the use of each tape! I don't want you accidently taking the wrong tapes or taking one from the wrong pile...